In North America, the XM satellite radio broadcast has been conducted since 2001. FIG. 5 is a diagram for explaining an XM satellite radio broadcast system. As shown in FIG. 5, in the XM satellite radio broadcast, the same contents are transmitted by satellite waves SAT1 and SAT2 from two satellites 1 and 2 and a ground wave TERR from a ground repeater. If a receiver can receive at least one of the waves, the receiver can reproduce sound without sound interruption. The satellite waves SAT1 and SAT2 are QPSK-modulated and the ground wave TERR is MCM-modulated.
FIG. 6 is a diagram of a frequency band of the XM satellite radio broadcast. The XM satellite radio broadcast uses a frequency band in a bandwidth of 12.5 MHz from 2332.5 MHz to 2345.0 MHz. The frequency band is divided into six slots including an A slot of the satellite wave SAT1, an A slot of the satellite wave SAT2, an A slot of the ground wave TERR, a B slot of the satellite wave SAT1, a B slot of the satellite wave SAT2, and a B slot of the ground wave TERR. In the A slots, for example, contents of 1 to 60 ch are transmitted. In the B slots, for example, contents of 61 to 120 ch are transmitted. The same contents are transmitted or broadcast in three bands.
FIG. 7 is a diagram for explaining a reception area of the XM satellite radio broadcast. For the sake of reception of the XM satellite radio broadcast, ground repeaters are provided for areas where it is difficult to receive radio waves from the satellites 1 or 2. For example, an area E1 in the suburbs where there is no obstacle such as a high building can receive a satellite wave, an area E2 such as an urban district where it is impossible to receive the satellite wave can receive a ground wave, and the middle of the area E1 and the area E2 can receive the satellite wave and the ground wave. This allows users to view the broadcast in any locations in North America.
When there are broadcast waves adjacent to a broadcast wave intended to be received, it is likely that the adjacent broadcast waves (hereinafter referred to as “adjacent interference waves” as well) interfere with the broadcast wave intended to be received and a reception failure is caused to deteriorate sensitivity of reception. A technique for setting a bandwidth of a pass band of a filter, which determines a reception signal band, in a narrow band to prevent this reception failure due to the adjacent interference waves is well known (see, for example, Patent Document 1).
Patent Document 1: Published Japanese Translation of a PCT patent application No. 8-504549